Hydrocarbon absorbing air filter box

ABSTRACT

A hydrocarbon absorbing air filter box is provided for absorbing evaporative hydrocarbon emissions from an air intake duct of an internal combustion engine. A combined mass airflow sensor and hydrocarbon trap comprising the hydrocarbon absorbing air filter box includes a duct supporting a hydrocarbon absorbing sheet within an interior of a housing. The duct communicates an airstream from an air filter to the air intake duct during operation of the internal combustion engine. An opening in the housing receives a mass airflow sensor into the duct, such that the mass airflow sensor is disposed within the airstream. Guide vanes extending across the duct reduce air turbulence within the airstream passing by the mass airflow sensor. Ports disposed along the duct allow the evaporative hydrocarbon emissions to be drawn into the interior and arrested by the hydrocarbon absorbing sheet when the internal combustion engine is not operating.

PRIORITY

This application claims the benefit of and priority to U.S. Provisional Application, entitled “Hydrocarbon Absorbing Air Filter Box,” filed on Oct. 27, 2018 and having application Ser. No. 62/751,581.

FIELD

The field of the present disclosure generally relates to engine air intake systems. More particularly, the field of the invention relates to an apparatus and methods for a hydrocarbon absorbing air filter box that exhibits a low resistance to airflow and arrests evaporative hydrocarbon emissions from an intake manifold of an internal combustion engine after engine shutdown.

BACKGROUND

An air intake filter removes particulate matter from air entering an air intake manifold of a motor vehicle. A variety of filter shapes have evolved over time for this purpose, such as flat panel, ring, cylindrical and frustoconical (section of a cone) designs. While air filters have largely served the purpose of removing particulate matter, such as dirt or debris, from the air entering the air intake manifold, such filters provide little help in preventing evaporative emissions from leaking out of the intake manifold and entering the atmosphere. Such emissions, arising chiefly when the engine is turned off and the intake manifold is hot, are a well-known contributor to air pollution.

During operation of an internal combustion engine, an airflow is drawn through the air intake system into an intake manifold and then finally into combustion chambers of the engine. The airflow is caused by the intake stroke of pistons within the engine, which foams an internal pressure within the intake manifold that is lower than the atmospheric pressure of the environment, and thus outside air is drawn into the air intake system. Evaporative emissions are prevented from exiting the air intake system due to the low internal pressure within the intake manifold and the airflow into the air intake system during operation of the internal combustion engine.

After engine shut-down, air continues to rush through the air intake system until the internal pressure within the intake manifold equals the atmospheric pressure of the environment. Evaporative hydrocarbons may be emitted if un-combusted fuel is present in the air intake system, such as due to pressurized fuel leaking from fuel rail(s) into the intake manifold through fuel injectors. This small amount of fuel may vaporize, and the resulting hydrocarbon vapor may migrate out of the air intake system into the atmosphere. Although such hydrocarbon vapor egress was once considered negligible, current regulations and environmental awareness have created a desire to eliminate evaporative emissions from the air intake systems of internal combustion engines.

Attempts to eliminate evaporative hydrocarbon emissions have included placing secondary, hydrocarbon adsorbing filters directly across the path of airflow into the air intake system. As will be appreciated, however, disposing extra layers of filtration media across the airflow path causes an additional flow restriction to be placed onto the air intake system. As such, the internal combustion engine is generally less efficient, or the air intake system may need to be increased in size so as to compensate for the increased flow restriction.

Other attempts to eliminate evaporative hydrocarbon emissions have included combining hydrocarbon vapor-adsorbing materials with conventional air filters. One drawback associated with these combination filters includes vapor-adsorbing materials flaking out of the combination filter and entering the air intake system. Further, such a loss of vapor-adsorbing materials may adversely affect the vapor absorbance of the combination filter. Accordingly, there is a need for eliminating hydrocarbon leakage from air intake systems of internal combustion engines without adversely affecting engine performance.

SUMMARY

A hydrocarbon absorbing air filter box and methods are provided for absorbing evaporative hydrocarbon emissions from an air intake duct of an internal combustion engine. The hydrocarbon absorbing air filter box comprises a combined mass airflow sensor and hydrocarbon trap for absorbing the evaporative hydrocarbon emissions. The combined mass airflow sensor and hydrocarbon trap comprises a housing that is configured to support a duct and at least one hydrocarbon absorbing sheet within an interior of the housing. The duct is configured to communicate an airstream from an air filter to the air intake duct during operation of the internal combustion engine. A mounting surface of the housing is configured to mate with, and be fastened to, a substantially similar surface disposed on the air filter box that contains the air filter. The housing comprises an opening that is configured to receive a mass airflow sensor into the duct, such that the mass airflow sensor is disposed within the airstream. A pair of guide vanes extend across the duct and are configured to reduce air turbulence within the airstream passing adjacent to the mass airflow sensor through the duct. At least one support comprising the duct is configured to maintain the hydrocarbon absorbing sheet disposed in an unfolded configuration adjacent to an inner perimeter surface of the housing. The shape of the support matches the shape of the interior, and the support has a size that provides clearance for the hydrocarbon absorbing sheet to be disposed between the edges of the support and the inner perimeter surface. A multiplicity of ports disposed along the duct are configured to allow the evaporative hydrocarbon emissions to be drawn into the interior and arrested by the hydrocarbon absorbing sheet when the internal combustion engine is not operating.

In an exemplary embodiment, a hydrocarbon absorbing air filter box for arresting evaporative hydrocarbon emissions from an air intake duct of an internal combustion engine comprises: a housing including at least one air inlet for communicating an airstream into an interior of the housing; an air filter supported within the interior for removing particulate matter from the airstream; and a combined mass airflow sensor and hydrocarbon trap configured to communicate the airstream from the air filter to the air intake duct.

In another exemplary embodiment, the combined mass airflow sensor and hydrocarbon trap includes at least one hydrocarbon absorbing sheet for absorbing evaporative hydrocarbon emissions emanating from the air intake duct. In another exemplary embodiment, the combined mass airflow sensor and hydrocarbon trap includes a duct configured for communicating the airstream from the air filter to the air intake duct. In another exemplary embodiment, the duct includes a multiplicity of ports configured to allow the evaporative hydrocarbon emissions to be drawn into an interior of the combined mass airflow sensor and hydrocarbon trap and captured by the at least one hydrocarbon absorbing sheet.

In another exemplary embodiment, the combined mass airflow sensor and hydrocarbon trap includes a duct for communicating the airstream from the air filter to the air intake duct. In another exemplary embodiment, the duct includes at least one support having a shape that matches the shape of an interior of the combined mass airflow sensor and hydrocarbon trap, and wherein the at least one support has a size that provides clearance for a hydrocarbon absorbing sheet to be disposed between the edges of the at least one support and an inner perimeter surface of the interior of the combined mass airflow sensor and hydrocarbon trap. In another exemplary embodiment, a housing comprising the combined mass airflow sensor and hydrocarbon trap is configured to be coupled with the hydrocarbon absorbing air filter box, such that the airstream is communicated through the duct during operation of the internal combustion engine. In another exemplary embodiment, the housing comprises a mounting surface that is configured to mate with a substantially similar surface disposed on the hydrocarbon absorbing air filter box, one or more holes disposed in the mounting surface being configured to receive fasteners suitable for coupling the housing and the hydrocarbon absorbing air filter box. In another exemplary embodiment, the housing comprises an opening that is configured to receive a mass airflow sensor into the interior of the combined mass airflow sensor and hydrocarbon trap, such that the mass airflow sensor is disposed within the airstream. In another exemplary embodiment, a channel is disposed within the duct and a separation comprising the hydrocarbon absorbing sheet are configured to accommodate the mass airflow sensor during assembling the combined mass airflow sensor and hydrocarbon trap.

In another exemplary embodiment, the combined mass airflow sensor and hydrocarbon trap comprises: a housing coupled with the air filter; a duct disposed within the housing to communicate the airstream from the air filter to the air intake duct; and a hydrocarbon absorbing sheet disposed between the duct and the housing to arrest evaporative hydrocarbon emissions from the air intake duct.

In another exemplary embodiment, the duct includes at least one support configured to maintain the hydrocarbon absorbing sheet disposed in an unfolded configuration adjacent to an inner perimeter surface of the housing. In another exemplary embodiment, the duct includes a multiplicity of ports configured to allow the evaporative hydrocarbon emissions to be drawn from the air intake duct to the hydrocarbon absorbing sheet within the housing. In another exemplary embodiment, the duct includes at least one pair of guide vanes that extend across an interior of the duct adjacent to the mass airflow sensor and are configured to reduce air turbulence within the airstream. In another exemplary embodiment, the housing includes an opening to receive the mass airflow sensor, such that the mass airflow sensor is disposed within the airstream.

In an exemplary embodiment, a method for arresting evaporative hydrocarbon emissions emanating from an air intake duct of an internal combustion engine comprises: forming a housing that includes at least one air inlet for communicating an airstream into an interior of the housing; supporting an air filter within the interior for removing particulate matter from the airstream; coupling a hydrocarbon trap with the air filter for communicating the airstream from the air filter to the air intake duct; disposing a hydrocarbon absorbing sheet within the hydrocarbon trap for absorbing the evaporative hydrocarbon emissions; and combining a mass airflow sensor with the hydrocarbon trap.

In another exemplary embodiment, disposing includes supporting the hydrocarbon sheet in an unfolded configuration within an interior of the combined mass airflow sensor and hydrocarbon trap. In another exemplary embodiment, coupling includes configuring a duct within the hydrocarbon trap to communicate the airstream through the hydrocarbon trap to the air intake duct. In another exemplary embodiment, configuring the duct includes forming a multiplicity of ports along the duct to allow the evaporative hydrocarbon emissions to be drawn to the hydrocarbon absorbing sheet. In another exemplary embodiment, combining includes configuring an opening in the hydrocarbon trap to receive the mass airflow sensor, such that the mass airflow sensor is disposed within the airstream. In another exemplary embodiment, combining includes disposing guide vanes adjacent to the mass airflow sensor to reduce air turbulence within the airstream.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings refer to embodiments of the present disclosure in which:

FIG. 1 illustrates an upper perspective view of an exemplary embodiment of a hydrocarbon absorbing air filter box according to the present disclosure;

FIG. 2 illustrates a lower perspective view of the hydrocarbon absorbing air filter box of FIG. 1 in accordance with the present disclosure;

FIG. 3 illustrates a first exploded view of an exemplary embodiment of a combined mass airflow sensor and hydrocarbon trap;

FIG. 4 illustrates a second exploded view of the combined mass airflow sensor and hydrocarbon trap of FIG. 3;

FIG. 5 illustrates a side plan view of an exemplary embodiment of a combined mass airflow sensor and hydrocarbon trap; and

FIG. 6 illustrates a rear plan view of the combined mass airflow sensor and hydrocarbon trap of FIG. 5.

While the present disclosure is subject to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. The invention should be understood to not be limited to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, to one of ordinary skill in the art that the invention disclosed herein may be practiced without these specific details. In other instances, specific numeric references such as “first filter medium,” may be made. However, the specific numeric reference should not be interpreted as a literal sequential order but rather interpreted that the “first filter medium” is different than a “second filter medium.” Thus, the specific details set forth are merely exemplary. The specific details may be varied from and still be contemplated to be within the spirit and scope of the present disclosure. The term “coupled” is defined as meaning connected either directly to the component or indirectly to the component through another component. Further, as used herein, the terms “about,” “approximately,” or “substantially” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein.

While air filters effectively remove particulate matter from air entering an air intake manifold of a vehicle engine, such filters provide little help in preventing evaporative emissions from leaking out of the intake manifold and entering the atmosphere when the engine is turned off. Evaporative emissions are a well-known contributor to air pollution. Attempts to eliminate evaporative hydrocarbon emissions have included placing secondary, hydrocarbon adsorbing filters directly across the path of airflow into the air intake system. However, disposing extra layers of filtration media across the airflow path causes an additional flow restriction that decreases engine efficiency. Other attempts to eliminate evaporative hydrocarbon emissions have included combining hydrocarbon vapor-adsorbing materials with conventional air filters. One drawback associated with these combination filters includes vapor-adsorbing materials flaking out of the combination filter and entering the air intake system, thereby adversely affecting the vapor absorbance of the combination filter. Embodiments presented herein provide a hydrocarbon absorbing air filter box that exhibits a low resistance to airflow and arrests evaporative hydrocarbon emissions from an intake manifold of an internal combustion engine after engine shutdown.

FIG. 1 illustrates an upper perspective view of an exemplary embodiment of a lower portion of an air filter box 100 that contains an air filter 104 coupled with a combined mass airflow sensor and hydrocarbon trap 108 (hereinafter, “hydrocarbon trap”) in accordance with the present disclosure. The air filter box 100 is comprised of at least one air inlet 112, shown in FIG. 2, that communicates an airstream 116 into an interior 120 of the air filter box by way of a duct 124. The air filter 104 is disposed within the interior 120 and configured to remove particulate matter and contaminants that may be flowing with the airstream 116 before the airstream passes through the hydrocarbon trap 108 and then is directed through a conduit 128 to an air intake duct of the internal combustion engine. The hydrocarbon trap 108 is configured to absorb evaporative hydrocarbon emissions leaking from the air intake duct when the internal combustion engine is not operating.

The air filter box 100 generally is comprised of a housing 132 that is configured to improve movement of the airstream 116 through the air filter 104. The housing 132 is configured to support the air filter 104 and provide an interface between an interior of the air filter and the air intake duct of the engine. It is contemplated that various techniques may be employed to couple the air filter 104 with the interior 120 of the housing 132, without limitation. For example, the housing 132 may include a mount portion that facilitates coupling the air filter 104 with an interior surface of the housing, thereby establishing an air-leak resistant connection between the interior of the air filter 104 and the air intake duct of the engine. The housing 132 preferably is comprised of a material that is sufficiently durable and temperature resistant to retain its configuration during operation when coupled with the air intake duct of the engine. It is envisioned that the housing 132 may be formed by way of injection molding, or other similar technique.

FIGS. 3-4 illustrate exploded views of an exemplary embodiment of the hydrocarbon trap 108 that may be coupled with the air filter box 100 according to the present disclosure. The hydrocarbon trap 108 is comprised of a housing 136 that supports a duct 140 and at least one hydrocarbon absorbing sheet 144 within an interior 148 of the housing. The duct 140 is comprised of two or more supports 152 that are configured to maintain the hydrocarbon absorbing sheet 144 disposed in a smooth, unfolded configuration adjacent to an inner perimeter surface 156 of the housing 136. The supports 152 generally have a shape that matches the shape of the interior 148, and have a size that provides enough clearance for the hydrocarbon absorbing sheet 144 to be disposed between the edges of the supports 152 and the inner perimeter surface 156, as best shown in FIG. 4. The supports 152 may be fabricated as extended portions of the duct 140 in the form of an individual component, or may be comprised of separate components that may be coupled with the duct 140.

A multiplicity of ports 160 disposed along the duct 140 are configured to allow evaporative hydrocarbon emissions to be drawn to, and arrested by the hydrocarbon absorbing sheet 144 when the engine is not operating. As best shown in FIG. 4, the ports 160 may be comprised of narrow openings within the duct 140 that allow evaporative hydrocarbon emissions to migrate into the interior 148, between the supports 152. It should be understood, however, that the ports 160 are not to be limited to narrow openings, but rather the ports 160 may be comprised of shaped openings other than the narrow openings illustrating in FIG. 4. Further, it is envisioned that, in some embodiments, any of various shaped portions, ridges, channels, ducts, and any other surface features, may be incorporated into the duct 140 and coupled with the ports 160, as is deemed beneficial to the evaporation of hydrocarbon emissions, without limitation.

The duct 140 is configured to direct the airstream 116 through the hydrocarbon trap 108 while the engine is operating. As such, the duct 140 comprises a flange 164 that is configured to be coupled with the air filter 104. The flange 164 may be directly received into a base of the air filter 104, or may be coupled with a tube, duct, or adapter comprising a portion of the air box 100 that receives the air filter 104. Further, the housing 136 comprises a mounting surface 168 and multiple holes 172 that are configured to enable fastening the hydrocarbon trap 108 onto the air filter box 100 so as to place the flange 164 into fluid communication with the interior of the air filter 104, as described herein. It is contemplated that the mounting surface 168 may be configured to mate with a substantially similar surface disposed on the air filter box 100. A suitable gasket may be positioned between the mounting surface 168 and the surface on the air filter box 100 so as to provide an air-leak resistant joint between the air filter 104 and the air intake duct of the engine.

As best shown in FIG. 4, the housing 136 comprises an opening 176 that is configured to receive a mass airflow sensor 180 into the hydrocarbon trap 108. As best shown in FIG. 5, the opening 176 facilitates fastening the mass airflow sensor 180 onto the housing 136, such that the mass airflow sensor 180 extends into the center of the duct 140, as shown in FIG. 6, and may be placed into contact with the airstream 116. A channel 184 disposed within the duct 140 and a separation 188 comprising the hydrocarbon absorbing sheet 144 are configured to accommodate the mass airflow sensor 180 during assembly of the hydrocarbon trap 108. For example, the channel 184 and separation 188 may facilitate inserting the duct 140 and hydrocarbon absorbing sheet 144 into the housing 136 after the mass airflow sensor 180 has been inserted into the opening 176 and fastened onto the housing 136. It is contemplated that the channel 184 and separation 188 may facilitate periodically removing and replacing the hydrocarbon absorbing sheet 144 without necessitating removal of the mass airflow sensor 180 from the housing 136. In some embodiments, however, any of various suitably sized openings may be disposed in the duct 140 and hydrocarbon absorbing sheet 144, in lieu of the channel 184 and separation 188, and configured to receive the mass airflow sensor 180.

As best shown in FIGS. 3 and 6, the duct 140 comprises at least a pair of guide vanes 192 that extend across an interior of the duct and adjacent to the mass airflow sensor 180. The guide vanes 192 are configured to advantageously reduce air turbulence within the airstream 116 passing by the mass airflow sensor 180 during operation of the engine. It is contemplated that reducing turbulence of the airstream 116 passing by the mass airflow sensor 180 may provide relatively greater accuracy of air flow measurements. As shown in FIG. 6, the mass airflow sensor 180 may be disposed between the guide vanes 192, such that the airstream 116 assumes a relatively laminar flow on both sides of the mass airflow sensor. In some embodiments, the guide vanes 192 may be molded as a portion of the duct 140, or the guide vanes 192 may comprise separate components that may be coupled with the duct 140, without limitation. It is contemplated that any of various structures may be implemented, in lieu of the guide vanes 192, as may be found to advantageously reduce turbulence in the airstream 116, without limitation.

While the invention has been described in terms of particular variations and illustrative figures, those of ordinary skill in the art will recognize that the invention is not limited to the variations or figures described. In addition, where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. To the extent there are variations of the invention, which are within the spirit of the disclosure or equivalent to the inventions found in the claims, it is the intent that this patent will cover those variations as well. Therefore, the present disclosure is to be understood as not limited by the specific embodiments described herein, but only by scope of the appended claims. 

What is claimed is:
 1. A hydrocarbon absorbing air filter box for arresting evaporative hydrocarbon emissions from an air intake duct of an internal combustion engine, the hydrocarbon absorbing air filter box comprising: a housing including at least one air inlet for communicating an airstream into an interior of the housing; an air filter supported within the interior for removing particulate matter from the airstream; and a combined mass airflow sensor and hydrocarbon trap configured to communicate the airstream from the air filter to the air intake duct.
 2. The hydrocarbon absorbing air filter box of claim 1, wherein the combined mass airflow sensor and hydrocarbon trap includes at least one hydrocarbon absorbing sheet for absorbing evaporative hydrocarbon emissions emanating from the air intake duct.
 3. The hydrocarbon absorbing air filter box of claim 2, wherein the combined mass airflow sensor and hydrocarbon trap includes a duct configured for communicating the airstream from the air filter to the air intake duct.
 4. The hydrocarbon absorbing air filter box of claim 3, wherein the duct includes a multiplicity of ports configured to allow the evaporative hydrocarbon emissions to be drawn into an interior of the combined mass airflow sensor and hydrocarbon trap and captured by the at least one hydrocarbon absorbing sheet.
 5. The hydrocarbon absorbing air filter box of claim 1, wherein the combined mass airflow sensor and hydrocarbon trap includes a duct for communicating the airstream from the air filter to the air intake duct.
 6. The hydrocarbon absorbing air filter box of claim 5, wherein the duct includes at least one support having a shape that matches the shape of an interior of the combined mass airflow sensor and hydrocarbon trap, and wherein the at least one support has a size that provides clearance for a hydrocarbon absorbing sheet to be disposed between the edges of the at least one support and an inner perimeter surface of the interior of the combined mass airflow sensor and hydrocarbon trap.
 7. The hydrocarbon absorbing air filter box of claim 6, wherein a housing comprising the combined mass airflow sensor and hydrocarbon trap is configured to be coupled with the hydrocarbon absorbing air filter box, such that the airstream is communicated through the duct during operation of the internal combustion engine.
 8. The hydrocarbon absorbing air filter box of claim 7, wherein the housing comprises a mounting surface that is configured to mate with a substantially similar surface disposed on the hydrocarbon absorbing air filter box, one or more holes disposed in the mounting surface being configured to receive fasteners suitable for coupling the housing and the hydrocarbon absorbing air filter box.
 9. The hydrocarbon absorbing air filter box of claim 7, wherein the housing comprises an opening that is configured to receive a mass airflow sensor into the interior of the combined mass airflow sensor and hydrocarbon trap, such that the mass airflow sensor is disposed within the airstream.
 10. The hydrocarbon absorbing air filter box of claim 7, wherein a channel is disposed within the duct and a separation comprising the hydrocarbon absorbing sheet are configured to accommodate the mass airflow sensor during assembling the combined mass airflow sensor and hydrocarbon trap.
 11. The hydrocarbon absorbing air filter box of claim 1, wherein the combined mass airflow sensor and hydrocarbon trap comprises: a housing coupled with the air filter; a duct disposed within the housing to communicate the airstream from the air filter to the air intake duct; and a hydrocarbon absorbing sheet disposed between the duct and the housing to arrest evaporative hydrocarbon emissions from the air intake duct.
 12. The hydrocarbon absorbing air filter box of claim 11, wherein the duct includes at least one support configured to maintain the hydrocarbon absorbing sheet disposed in an unfolded configuration adjacent to an inner perimeter surface of the housing.
 13. The hydrocarbon absorbing air filter box of claim 11, wherein the duct includes a multiplicity of ports configured to allow the evaporative hydrocarbon emissions to be drawn from the air intake duct to the hydrocarbon absorbing sheet within the housing.
 14. The hydrocarbon absorbing air filter box of claim 11, wherein the duct includes at least one pair of guide vanes that extend across an interior of the duct adjacent to the mass airflow sensor and are configured to reduce air turbulence within the airstream.
 15. The hydrocarbon absorbing air filter box of claim 11, wherein the housing includes an opening to receive the mass airflow sensor, such that the mass airflow sensor is disposed within the airstream.
 16. A method for arresting evaporative hydrocarbon emissions emanating from an air intake duct of an internal combustion engine, the method comprising: forming a housing that includes at least one air inlet for communicating an airstream into an interior of the housing; supporting an air filter within the interior for removing particulate matter from the airstream; coupling a hydrocarbon trap with the air filter for communicating the airstream from the air filter to the air intake duct; disposing a hydrocarbon absorbing sheet within the hydrocarbon trap for absorbing the evaporative hydrocarbon emissions; and combining a mass airflow sensor with the hydrocarbon trap.
 17. The method of claim 16, wherein disposing includes supporting the hydrocarbon sheet in an unfolded configuration within an interior of the combined mass airflow sensor and hydrocarbon trap.
 18. The method of claim 16, wherein coupling includes configuring a duct within the hydrocarbon trap to communicate the airstream through the hydrocarbon trap to the air intake duct.
 19. The method of claim 18, wherein configuring the duct includes forming a multiplicity of ports along the duct to allow the evaporative hydrocarbon emissions to be drawn to the hydrocarbon absorbing sheet.
 20. The method of claim 16, wherein combining includes configuring an opening in the hydrocarbon trap to receive the mass airflow sensor, such that the mass airflow sensor is disposed within the airstream.
 21. The method of claim 16, wherein combining includes disposing guide vanes adjacent to the mass airflow sensor to reduce air turbulence within the airstream. 